Polyvinyl chloride is widely used for wire insulation and plenum cable jacketing because of its insulating and flame and smoke retardant properties. For example, it has been recognized that the use of polyvinyl chloride in wire insulations and cable jacketing reduces the hazards of flammability, toxic decomposition and smoke in the event of a fire. In addition, polyvinyl chloride is especially desirable because of its low cost. Likewise, the use of fluorocarbon for similar purposes is a viable alternative to polyvinyl chloride but is not as desirable due to its relatively high cost.
To date, there are presently several polyvinyl based compositions that are used to insulate wires and cables, including U.S. Pat. No. 4,892,683 which discloses a composition that includes chlorinated polyvinyl chloride or chlorinated polyethylene and U.S. Pat. No. 4,670,494 which discloses a composition that includes chlorinated polyvinyl chloride. The aforementioned patents, however, generally require chlorinated polyvinyl chloride (CPVC) and chlorinated polyethylene (CPE) as an essential ingredient and generally have inferior flame and smoke retardant properties.
While the previously mentioned polyvinyl and fluorocarbon compositions are relatively adequate flame retardants and insulators, there are problems associated with their use. One such problem is that the known compositions generally include high levels of plasticizers which are necessary for flexibility and good processing properties but which generally increase the flammability of the polyvinyl chloride compositions. Another problem is that these compositions process slower and therefore, decrease the output of cable. In addition, these known compositions have approximately 30% more spark test failures.